1. Fields of the Invention
The present invention relates to an auto back-up unit, and more particularly, to a seat backrest auto back-up unit which automatically backs the backrest upright when the user leaves the seat.
2. Descriptions of Related Art
The conventional seats in public sites such as theaters, performance centers, bus stations or airports are arranged in rows and the distance between the front row and the rear row usually fixed. The backrest of the seat is positioned at an angle relative the seat portion. However, the inclined backrest reduces the distance between the front and rear rows of the seats and also restricts the speed for the users to leave from the public sites. The limited distance between the front and rear rows of the seats can be a problem during in emergent situations.
Taiwan Publication No. 424460 discloses a folding mechanism for a seat, wherein the seat portion is pivotably connected between two armrests and a weight is connected to the rear side of the seat portion. When the seat is empty, the seat portion is automatically pivoted upward. A U-shaped link is connected on the weight and is fixed to a curved guide plate under the backrest. The mediate portion of the backrest is pivotably connected to the seat frame so that when the user leaves from the seat portion, the seat portion pivots upward and the U-shaped link pushes the curved guide plate to back up the backrest so that the space between the front and rear rows of the seats is maintained the expected width.
Taiwan Publication No. 472546 discloses an auto back-up mechanism for a seat, and comprises a base fixed on the floor and a pressing member fixed to the base. The pressing member has a compression section. A seat pad is pivotably connected to the base by a pivot so that the seat pad is positioned at a first position and a second position. The pivot has an eccentric section which is compressed by the compression section so as to keep the seat pad at the first position. When applying a force to the seat pad to pivot the seat pad toward the second position, the eccentric section receives a reaction force from the compression section in reverse direction.
Taiwan Publication No. 476263 discloses a mechanism for folding a seat, and comprises two L-shaped frames, the upright portions of the frames are connected to the backrest and the horizontal portions of the frames are connected to the seat portion. A hole is defined in the mediate portion of each of the frames and two bases each have a pivot which is pivotably connected to the hole. A slot is defined in the horizontal portion. A resilient member is connected between the pivot and a pin on the front end of the horizontal portion. When the user rests on the backrest, the frames swing backward, and the horizontal portion slides along the slot and the resilient member is stretched and contacts the end of the slot to restrict the angle that the horizontal portion slides. The resilient member moves the horizontal portion back when the user leaves from the seat.
U.S. Pat. Nos. 2,492,107, 5,918,937 and 1,29,413 disclose a mechanism between the seat portion and the backrest and/or armrests so that when folding the seat, the backrest is pivoted to a desired position of angle. The backrest can be positioned at the upright position when the user leaves from the seat to maintain the distance between the seats, however, the mechanism is complicated and takes a lot of time to be assembled. The maintenance cost is high and too many parts are involved.
The present invention intends to provide an auto back-up unit for a seat and which improves the shortcomings of the present invention.